JP4608729B2 - Biaxially stretched colored polyester film for laminating metal plates - Google Patents

Description

なお、表中の記号は次の通りである。
ＰＥＴ：ポリエチレンテレフタレート
ＰＥＴ／Ｉ：イソフタル酸（５モル％）共重合ポリエチレンテレフタレート
ＰＥＴ／Ａ：アジピン酸（１５モル％）共重合ポリエチレンテレフタレート
【００５２】
【発明の効果】
本発明によると、金属板と貼合せて成形加工されることにより美麗性に優れた金属缶類を製造でき、かつ、耐熱性、加工性に優れた金属板貼合せ用二軸延伸着色ポリエステルフィルムを提供することができる。
【００５３】
そして、本発明のフィルムを金属板にラミネートさせたラミネート鋼板は美麗性及び成形加工性に優れるので、美麗性及び外観に優れた金属缶類を容易に製造することが可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially stretched colored polyester film for laminating metal plates, and in particular, being laminated and processed with a steel or aluminum plate and used as a laminating material on the outer surface side of metal cans and metal can lids. Therefore, the present invention relates to a biaxially stretched colored polyester film for laminating metal plates, which can exhibit excellent aesthetics and is excellent in heat resistance and workability.
[0002]
[Prior art]
Metal cans are widely used in the world and are indispensable for our lives. In the past, curable resin was applied to a metal plate and cured, but in recent years, in order to obtain a metal can that is environmentally friendly and excellent in hygiene, for example, a copolyester film is made of steel or aluminum. A method of manufacturing a metal can by being bonded to a plate and processed. Furthermore, in the case of beverage cans, for the sake of beauty and display, the outer surface of the can body is printed, a film to which a white pigment is added is pasted, or a color-printed film is pasted. A method such as combining is adopted. However, when there are parts that are not printed on metal cans, or when a film that is not subjected to white pigment addition or full surface printing is bonded, the color of the metal is exposed as an appearance, and the beauty is poor. Become. In particular, food cans and the like are often larger in the area of the lid and the bottom than the cans, so that the metal color is exposed as it is and the aesthetic appearance is often impaired.
[0003]
[Problems to be solved by the invention]
However, further color printing or the like on the exposed portion of the metal color increases the number of steps and decreases the productivity. Moreover, even if a pre-printed film is pasted and processed on a metal plate, it is difficult to give the film the necessary formability when forming the metal plate into a shape such as a can body part or a lid. It was difficult for the film to retain sufficient formability and printability to be applied to the application.
[0004]
Therefore, the present invention is a metal that exhibits excellent laminating properties and moldability, has a specific color tone that is not found in conventional polyester films, and is molded and bonded to a metal plate. An object of the present invention is to provide a biaxially stretched colored polyester film for laminating metal plates that can produce cans and is excellent in heat resistance and workability.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the biaxially stretched colored polyester film for laminating a metal plate of the present invention comprises a polyester mainly composed of an ethylene terephthalate unit and / or an ethylene naphthalate unit, Containing 0.1 to 50% by weight of one or more colorants of anthraquinone and benzimidazolone, It has a color tone with a value of 1 to 30 and b value of 15 to 45 according to the method of JIS Z-8722, and the carboxyl end group is 30 to 55 equivalent / ton.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The polyester mainly comprising an ethylene terephthalate unit and / or an ethylene naphthalate unit in the present invention is a polyester having 70% by mole or more of an ethylene terephthalate unit and / or an ethylene naphthalate unit, from the viewpoint of heat resistance and the like. It is preferably 85 mol% or more, more preferably 95 mol% or more. Other dicarboxylic acid components and glycol components may be copolymerized. Examples of the dicarboxylic acid component include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5- Aromatic dicarboxylic acids such as sodium sulfoisophthalic acid and phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, and cyclohexyne dicarboxylic acid An oxycarboxylic acid such as an aromatic dicarboxylic acid or p-oxybenzoic acid can be used. On the other hand, examples of the glycol component include aliphatic glycols such as propanediol, butanediol, pentanediol, hexanediol and neopentyl glycol, and alicyclic glycols such as cyclohexanedimethanol. Aromatic glycols such as bisphenol A and bisphenol S, diethylene glycol and the like can be used. Two or more of these dicarboxylic acid components and glycol components can be used in combination.
[0007]
In addition, a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane can be copolymerized with the copolymerized polyester as long as the effects of the present invention are not impaired.
[0008]
Preferable components copolymerized in a small amount with the polyester used in the present invention are butanediol, diethylene glycol, polyethylene glycol, cyclohexanedimethanol, sebacic acid, adipic acid, dimer acid, isophthalic acid, and naphthalenedicarboxylic acid component.
[0009]
Moreover, in this invention, it is preferable that melting | fusing point is 246 degreeC or more and 280 degrees C or less, More preferably, it is 248 degreeC or more and 275 degrees C or less at the point which suppresses the time-dependent change after a shaping | molding process.
[0010]
According to the method of JIS Z-8722, the film of the present invention needs to have a color tone having an a value of 0 to 50 and a b value of 10 to 50. By setting the a value and the b value within these ranges, after the film is bonded to the metal plate, a golden appearance is obtained and the beauty is excellent. Here, the a value is preferably 0.5 to 40, particularly preferably 1 to 30, and the b value is preferably 15 to 45, particularly preferably 20 to 40. Further, the L value is preferably 40 to 90 from the viewpoint of improving the appearance impression. Moreover, in order to make a value, b value, and L value into this range, the method of selecting colorants, such as an inorganic pigment, an organic pigment, and dye, and adding to a film is preferable.
[0011]
Furthermore, in this invention, it is preferable that the change rate (b1) of b value before and behind dry-heat-processing for 1 minute at 200 degreeC is 0 to 20%, More preferably, it is 0 to 10%. Moreover, it is preferable that the change rate (b2) of b value before and after retorting for 20 minutes at 120 degreeC is 0 to 20%, More preferably, it is 0 to 10%. In particular, the heat resistance of the colorant added to the film is important in order to use it suitably at high temperature or under retort. For example, the weight loss rate at 200 ° C is 5% or less, and at 300 ° C, it is 5% or less. It is preferable to use a certain colorant.
[0012]
Examples of the inorganic pigment used in the present invention include titanium oxide, calcium carbonate, barium sulfate, aluminum oxide, silicon dioxide, carbon black, iron oxide, chromium oxide, zinc white, lead white, bengara, cadmium red, yellow lead, cobalt There are blue, cobalt purple and zinc chromate. These inorganic pigments can be surface-treated with oxides such as aluminum, silicon and zinc in order to improve dispersibility and processability in polyester. Organic pigments include condensed azo, isoindolinone, perinone, quinacridone, diketopyrrolopyrrole, anthraquinone, dioxazine, benzimidazolone, copper phthalocyanine (β), metal complex azo, chlorinated copper phthalocyanine (α), allyl Amide, azo (Ca), diarylide AA, diarylide MX, diarylide HR, pyrazolone naphthol red, BON allylamide, 2B toner (Ca), 4B toner (Ca), copper phthalocyanine (α), halogenated copper phthalocyanine, naphthol, dioxazine Naphthol AS, diarylide OT, pyrazolone, lake red C (Ba), BON allylamide, and the like can be used. On the other hand, as the dye, chromium complex, cobalt complex, phthalocyanine, methine, anthraquinone and the like can be used. Two or more of these colorants can be used in combination. In the present invention, it is particularly preferable to use anthraquinone, quinacridone, benzimidazolone, and diketopyrrolopyrrole colorants.
[0013]
The colorant blended in the polyester film of the present invention may be added during the polymerization reaction of the polyester, and after polymerization, the colorant is kneaded and dispersed using, for example, a twin screw extruder to produce master pellets. In addition, a method of blending a predetermined amount of this into the polyester film may be employed. As a method for adjusting the content of the colorant, a master pellet containing a colorant at a high concentration is prepared by the above-described method, and a pellet containing substantially no colorant and the master pellet are mixed to obtain a predetermined level. A method of diluting to the colorant content is effective. The colorant may be subjected to treatments such as pulverization, dispersion, classification, and filtration in advance as necessary.
[0014]
The average particle diameter of the colorant is preferably 0.01 to 0.5 μm, more preferably 0.01 to 0.3 μm. If the average particle diameter exceeds 0.5 μm, the film surface may become too rough and difficult to print, or film defects are likely to occur, which is not preferable.
[0015]
The content of the colorant is preferably 0.1 to 50% by weight, and more preferably 1 to 20% by weight. If the content is less than 0.1% by weight, the entire film is easy to see through, and a desired color tone is difficult to appear. On the other hand, if it exceeds 50% by weight, the colorant tends to aggregate, resulting in a film defect, and the film strength tends to decrease. In particular, when an organic pigment or dye is used as a colorant, the content is preferably 1 to 25% by weight, more preferably 3 to 20% by weight, and still more preferably 5 to 15% by weight. If it exceeds 25% by weight, the color tone may change due to reduction of the colorant or the like due to thermal decomposition, thermal deterioration, sublimation, etc. in the drying or melt extrusion process.
[0016]
The film structure may be a two-layer A / B layer, a three-layer A / B / A or A / B / C layer, or a multilayer structure with more than three layers, and the layer thickness ratio may be set arbitrarily. It doesn't matter. The colorant-containing layer may be any one of the A layer, the B layer, and the C layer, or the entire layer may be the containing layer.
[0017]
In the present invention, it is necessary to biaxially stretch a polyester mainly composed of an ethylene terephthalate unit and / or an ethylene naphthalate unit from the viewpoints of heat resistance and impact resistance after processing. The biaxial stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching. As a biaxially stretched film, the average value of the elongation at break in the longitudinal direction and the elongation at break in the width direction at 100 ° C. is 200 to 500% from the viewpoint of handleability and workability in the production process and the like. Preferably, it is 250 to 450%. In order for workability to be uniform and good in each direction, the absolute value of the difference between the elongation at break in the longitudinal direction at 100 ° C. and the elongation at break in the width direction is preferably 50% or less. Preferably it is 40% or less.
Furthermore, the average value of the breaking elongation in the direction inclined 45 degrees clockwise from the longitudinal direction at 100 ° C. and the breaking elongation in the direction inclined 135 degrees is preferably 200 to 500% or less, more preferably. Is 250-450%. Further, the absolute value of the difference between the breaking elongation in the longitudinal direction at 100 ° C. and the breaking elongation in the direction inclined 45 degrees clockwise from the longitudinal direction is preferably 50% or less, particularly preferably 40% or less. is there.
[0018]
Here, the elongation at break was measured using a tensilon (tensile tester) at a pulling speed of 500 mm / min, a test piece having a width of 10 mm and a sample length of 50 mm in an atmosphere of 100 ° C. and 65%. (%).
[0019]
In the present invention, the intrinsic viscosity of the polyester is preferably 0.4 to 1.5 dl / g, more preferably 0.5 to 1.3 dl / g, and particularly preferably 0.6 to 1.5 in terms of processability and heat resistance. 1.2.
[0020]
In the present invention, the density of the film is 1.35 to 1.41 g / cm. ^Three Is preferable in terms of improving workability, and particularly preferably 1.36 to 1.4 g / cm. ^Three It is. If the density is too low, the moldability deteriorates due to wrinkles, and if the density is too high, the workability will vary.
[0021]
When producing the polyester used in the present invention, a reaction catalyst can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and the like. Can be used. Preferably, an antimony compound, a germanium compound, or a titanium compound is preferably added as a polymerization catalyst at any stage before the production of the polyester is completed. As such a method, for example, when a germanium compound is used, for example, a method of adding a germanium compound powder as it is, or as described in Japanese Patent Publication No. Sho 54-22234, a polyester starting material is used. Examples thereof include a method of dissolving a germanium compound in a glycol component and adding it. Examples of germanium compounds include germanium dioxide, germanium hydroxide containing crystal water, or germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethyleneglycoxide, germanium phenolate, germanium β- Germanium phenoxide compounds such as naphtholates, phosphorus-containing germanium compounds such as germanium phosphate and germanium phosphite, germanium acetate, and the like can be used. Of these, germanium dioxide is preferable. As the antimony compound, for example, antimony oxide such as antimony trioxide, antimony acetate, or the like can be used. As the titanium compound, alkyl titanate compounds such as tetraethyl titanate and tetrabutyl titanate are preferably used.
[0022]
For example, a case where germanium dioxide is added as a germanium compound when producing polyethylene terephthalate will be described. Transesterify or esterify the terephthalic acid component and ethylene glycol, then add germanium dioxide and phosphorus compound, then continue polycondensation reaction at high temperature and reduced pressure until a certain diethylene glycol content is reached. Get coalesced. Further preferably, the obtained polymer is subjected to a solid phase polymerization reaction under a reduced pressure or an inert gas atmosphere at a temperature below its melting point to reduce the acetaldehyde content to obtain a predetermined intrinsic viscosity and carboxyl end group. Etc.
[0023]
In the present invention, from the viewpoint of improving the compatibility between the polyester and the colorant, the amount of the carboxyl terminal group of the polyester is preferably 30 to 55 equivalent / ton, more preferably 35 to 50 equivalent / ton, and particularly preferably 40. -48 eq / ton.
[0024]
The polyester in the present invention preferably has a diethylene glycol component amount of 0.01 to 4% by weight, more preferably 0.01 to 3% by weight, and particularly preferably 0.01 to 2% by weight. It is desirable to maintain good hygiene even if it receives heat history during processing. Further, an antioxidant may be added in an amount of 0.0001 to 1% by weight. Further, diethylene glycol may be added during the production of the polymer as long as the characteristics are not impaired.
[0025]
In order to improve hygiene, the content of acetaldehyde in the film is preferably 30 ppm or less, more preferably 25 ppm or less, and particularly preferably 20 ppm or less. In order to reduce the content of acetaldehyde in the film to 30 pm or less, a method of removing acetaldehyde generated by thermal decomposition when the polyester is produced by a polycondensation reaction or the like may be used. A method of heat-treating at a temperature below the melting point of the polyester in a gas atmosphere, preferably a method of solid-phase polymerization of the polyester at a temperature of 150 ° C. or more and below the melting point in a reduced pressure or inert gas atmosphere, and a vacuum vent type extruder The melt extrusion method is used, and the extrusion temperature at the time of melt extrusion of the polymer is kept at the melting point + 30 ° C. or less, preferably the melting point + 25 ° C. or less on the high melting point polymer side, and is pushed for a short time, preferably within an average residence time of 1 hour or less. What is necessary is just to implement the method to take out.
[0026]
As a method for producing a biaxially stretched film in the present invention, for example, after drying each polyester as necessary, it is supplied to a known melt extruder, extruded from a slit die into a sheet, and a system such as electrostatic application Is brought into close contact with the casting drum and cooled and solidified to obtain an unstretched sheet. The stretching method may be either simultaneous biaxial or sequential biaxial stretching, but the unstretched sheet is stretched and heat-treated in the longitudinal direction and the width direction of the film to obtain a film having a desired degree of plane orientation. A tenter method is preferred from the viewpoint of film quality, and a sequential biaxial stretching method in which the film is stretched in the longitudinal direction and then stretched in the width direction, and a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are stretched almost simultaneously are desirable. . The draw ratio is 1.5 to 4.0 times in each direction, preferably 1.8 to 4.0 times. Either the stretching ratio in the longitudinal direction or the width direction may be increased or the stretching ratio may be the same. The stretching speed is desirably 1000% / min to 200000% / min, and the stretching temperature can be any temperature as long as it is not less than the glass transition temperature of the polyester and not less than the glass transition temperature + 80 ° C. 80-150 degreeC is preferable. Further, the film is heat-treated after biaxial stretching, and this heat treatment can be carried out by any conventionally known method such as on a heated roll in the oven. The heat treatment temperature can be any temperature of 120 ° C. or higher and 245 ° C. or lower, but is preferably 120 to 240 ° C. Moreover, although the heat processing time can be made arbitrary, it is preferable to carry out normally for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.
[0027]
Further, in order to improve the handleability and processability of the film of the present invention, particles arbitrarily selected from external particles such as internal particles, inorganic particles and / or organic particles having an average particle diameter of 0.01 to 10 μm Is preferably contained in an amount of 0.01 to 50% by weight. In particular, it is preferable as a film used on the inner surface of the can that 0.01 to 3 wt% of internal particles, inorganic particles and / or organic particles having an average particle diameter of 0.1 to 5 μm are contained. Examples of the method for precipitating the internal particles include the techniques described in JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, JP-A-54-90397, and the like. Can be mentioned. Further, other particles such as JP-A-55-20496 and JP-A-59-204617 can be used in combination. Use of particles having an average particle diameter exceeding 10 μm is not preferable because defects of the film are likely to occur. Examples of inorganic particles and / or organic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, and other styrene, silicone, acrylic, and the like. The organic particle etc. which contain acids etc. as a structural component can be mentioned. Among them, there can be mentioned inorganic particles such as wet and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components. These internal particles, inorganic particles and / or organic particles may be used in combination of two or more.
[0028]
Further, from the viewpoint of adhesion, the center line average roughness Ra is preferably 0.005 to 0.07 μm, and more preferably 0.008 to 0.05 μm. Furthermore, when the ratio Rt / Ra between the maximum roughness Rt and the centerline average roughness Ra is 4 to 50, preferably 6 to 40, high-speed can-making ability is improved.
[0029]
In addition, it is preferable to improve the adhesion to the metal plate by subjecting the film to a surface treatment such as a corona discharge treatment to further improve the properties. At that time, the processing strength is 5 to 50 W · min / m. ² , Preferably 10 to 45 W · min / m ² It is.
[0030]
In the polyester film of the present invention, additives such as an antistatic agent, a heat stabilizer, an antioxidant, a crystal nucleating agent, a weathering agent, and an ultraviolet absorber can be used as long as the object of the present invention is not impaired. Further, surface unevenness processing such as embossing and sand mat processing, or surface treatment such as corona discharge treatment, plasma treatment, and alkali treatment may be performed as necessary. In addition, the film of the present invention is easily treated with an adhesive, an antistatic agent, a water vapor / gas barrier agent (polyvinylidene chloride, etc.), a release agent, an adhesive, an adhesive, a flame retardant, an ultraviolet absorber, a matting agent, a pigment, Coating or printing of dyes may be performed, and metals such as aluminum, aluminum oxide, silicon oxide, palladium and their compounds may be vacuum-deposited for light shielding, water vapor / gas barrier, surface conductivity, infrared reflection, etc. The purpose and method are not limited to the above.
[0031]
Although the polyester film of this invention can be used conveniently as a film for metal plate bonding, it is preferable to use it for the outer surface of a metal can or a metal can lid from the point of aesthetics.
[0032]
[Measurement and evaluation methods of physical properties and characteristics]
The physical properties and characteristics measurement and evaluation methods used in the description of the present invention or in the examples described later will be described below.
[0033]
(1) Melting point (Tm)
It measured using the differential scanning calorimeter DSC2 (made by Perkin Elmer). 10 mg of the sump was melted and held at 280 ° C. for 5 minutes under a nitrogen stream, and then rapidly cooled with liquid nitrogen. In the process of raising the temperature of the obtained sample at a rate of 10 ° C./min, the endothermic peak temperature based on crystal melting was measured and taken as the melting point (Tm).
[0034]
(2) Film elongation -I, -II, -III
The breaking elongation in the longitudinal direction, the breaking elongation in the width direction, the breaking elongation in a direction inclined 45 degrees clockwise from the longitudinal direction, and the breaking elongation in a direction inclined 135 degrees clockwise from the longitudinal direction. Was measured at 100 ° C. by a method according to ASTM-D-882-81 (Method A). From each of these breaking elongations, the following values were obtained and ranked for each. Class A and class B are acceptable.
[0035]
(1) Film elongation-I = average value of elongation at break in the longitudinal direction and elongation at break in the width direction,
Class A: The average value is 300% or more and 500% or less
Class B: The average value is 200% or more and less than 300%
Class C: The average value is 0 to less than 200%
(2) Film elongation-II = absolute value of the difference between the breaking elongation in the longitudinal direction and the breaking elongation in the width direction,
Class A: The absolute value of the difference is 0 to less than 50%
Class B: absolute value of the difference is 50% or more and less than 100%
Class C: the absolute value of the difference is 100% or more
(3) Film elongation-III = average value of the breaking elongation in the direction inclined 45 degrees clockwise from the longitudinal direction and the breaking elongation in the direction inclined 135 degrees,
Class A: The average value is 300% or more and 500% or less
Class B: The average value is 200% or more and less than 300%
Class C: The average value is 0 to less than 200%
(3) Intrinsic viscosity (IV)
The polyester was dissolved in orthochlorophenol and measured at 25 ° C.
[0036]
(4) Color tone
Using a color analyzer (“TC-1800MKII type” manufactured by Tokyo Denshoku Co., Ltd.), the color tone was measured with the values of L, a, and b by the method of JIS Z-8722.
[0037]
(5) Heat resistance
The film was dry heat treated at 200 ° C. for 1 minute, and the absolute value of the difference between the b values before and after the treatment was divided by the b value before the treatment, and the value expressed as a percentage was defined as the change rate b1 (%). Based on that value, the ranking was as follows.
[0038]
Class A: 0 to 5% or less
Class B: 5-10% or less
Class C: Over 10%.
[0039]
(6) Retort resistance
The film was retorted at 120 ° C. for 20 minutes, the absolute value of the difference between the b values before and after the treatment was divided by the b value before the treatment, and the value expressed as a percentage was defined as the rate of change b2 (%). Based on that value, the ranking was as follows.
[0040]
Class A: 0 to 10% or less
Class B: 10 to 20% or less
Class C: Over 20%.
[0041]
(7) Workability of laminated steel sheet
Cans were formed from a steel sheet laminated with a film at a reduction rate of 30%, and ranked according to the state of the obtained cans as follows.
[0042]
A grade: There is no whitening, a crack, and an overlap wrinkle in a film.
[0043]
B grade: Overlapping and slight whitening are observed on the film, but there are no cracks.
[0044]
Class C: The film is whitened, cracked, and overlapped.
[0045]
【Example】
The following examples illustrate the invention.
[0046]
Example 1
After the ethylene glycol slurry containing the agglomerated silica particles is heat treated at 190 ° C. for 2 hours as polyester, the slurry is added and polycondensed at the stage after the esterification reaction in the polymerization process using an amorphous germanium catalyst. The reaction was carried out to produce a chip A of polyethylene terephthalate (containing an intrinsic viscosity of 0.65 and diethylene glycol of 2.8 mol%) containing 0.1% by weight of agglomerated silica particles having an average particle size of 1.4 μm. On the other hand, a colored master chip B in which 30% of an anthraquinone compound was added to the chip A was produced. Chip A and master chip B are vacuum dried at 180 ° C. for 3 hours, and then supplied to a single screw extruder. After discharging from a normal die, a mirror cooling drum (drum rotation speed) is applied while applying electrostatic force (7 kv). 40 m / min) to cool and solidify to obtain an unstretched film containing 10% of anthraquinone compound. This unstretched film was stretched 2.8 times in the longitudinal direction at a temperature of 105 ° C., cooled to 40 ° C., preheated at 115 ° C. for 5 seconds, stretched 2.8 times in the width direction at the same temperature, and then 180 ° C. 5% relaxed for 5 seconds, and a biaxially stretched colored polyester film having a thickness of 25 μm was obtained. Table 1 shows the characteristics of the obtained colored polyester film.
[0047]
The obtained film was laminated at 70 m / min on a TFS steel plate (thickness 0.2 mm) heated to its melting point + 30 ° C., and then rapidly cooled in a 50 ° C. water bath. The appearance of the obtained laminated steel sheet was golden and excellent in beauty, and the workability when forming into a can was good.
[0048]
Examples 2-3
Except having changed the kind and colorant of polyester, it formed into a film like Example 1 and the colored polyester film was obtained. The results are shown in Table 1. The appearance of the obtained film-laminated steel sheet was golden and had good aesthetics.
[0049]
Comparative Example 1
As polyester, after heat-treating an ethylene glycol slurry containing agglomerated silica particles at 190 ° C. for 2 hours, at the stage after completion of the esterification reaction in the polymerization process using an antimony catalyst, the above slurry is added, and a polycondensation reaction is performed. A chip of polyethylene terephthalate (containing 0.61 intrinsic viscosity and 3 mol% diethylene glycol) containing 0.1% by weight of agglomerated silica particles having an average particle size of 1.4 μm was manufactured. After vacuum drying at 180 ° C. for 3 hours, it is supplied to a single screw extruder, discharged from a normal die, cooled and solidified with a mirror cooling drum (drum rotation speed 40 m / min) while applying electrostatic force (7 kv), and unstretched A film was obtained. This unstretched film was stretched 3.4 times in the longitudinal direction at a temperature of 90 ° C, cooled to 40 ° C, preheated at 105 ° C for 5 seconds, stretched 3.5 times in the width direction at the same temperature, and then 220 ° C. A polyester film having a thickness of 25 μm that was biaxially stretched was obtained by heat treatment at 3% for 5 seconds. The results are shown in Table 1. The appearance of the obtained film-laminated steel plate was a steel plate color and inferior in beauty.
[0050]
Comparative Example 2
As a polyester, a polyester film was produced and evaluated in the same manner as in Comparative Example 1 except that polyethylene terephthalate copolymerized with 15 mol of adipic acid was used. As a result, the polyester film was inferior in heat resistance and beauty.
[0051]
[Table 1]

The symbols in the table are as follows.
PET: Polyethylene terephthalate
PET / I: Isophthalic acid (5 mol%) copolymerized polyethylene terephthalate
PET / A: adipic acid (15 mol%) copolymerized polyethylene terephthalate
[0052]
【The invention's effect】
According to the present invention, biaxially stretched colored polyester film for laminating metal plates, which can produce metal cans excellent in beauty by being laminated with a metal plate and is excellent in heat resistance and workability. Can be provided.
[0053]
And since the laminated steel plate which laminated | stacked the film of this invention on the metal plate is excellent in aesthetics and moldability, it becomes possible to manufacture easily the metal cans excellent in aesthetics and an external appearance.

Claims (5)

It consists of a polyester mainly composed of ethylene terephthalate units and / or ethylene naphthalate units, and contains 0.1 to 50% by weight of one or more colorants of anthraquinone and benzimidazolone, JIS Z Biaxial stretching for bonding metal plates characterized by having a color tone of 1 to 30 and b value of 15 to 45 by the method of -8722, and having carboxyl end groups of 30 to 55 equivalent / ton Colored polyester film. Melting | fusing point is 246-280 degreeC, The biaxially-stretched colored polyester film for metal plate bonding of Claim 1 characterized by the above-mentioned. The biaxially stretched colored polyester film for laminating metal sheets according to claim 1 or 2, wherein the change rate (b1) of the b value by dry heat treatment at 200 ° C for 1 minute is 0 to 20%. Biaxially stretched colored polyester for laminating metal sheets according to any one of claims 1 to 3, wherein the rate of change of b value (b2) by retorting at 120 ° C for 20 minutes is 0 to 20%. the film. The biaxially stretched colored polyester film for laminating metal plates according to any one of claims 1 to 4, which is used as a laminating material on the outer surface side of a metal can or a metal can lid.